The Renal System

Question 1

Outline the gross structure of the kidneys

Answer 1

Cortex, pyramids (medulla), renal artery, renal vein, calyces, renal pelvis, renal papilla, nephrons, collecting duct

Question 2

Describe nephron structure

Answer 2

Renal cortex- Afferent arteriole, efferent arteriole, glomerulus, glomerulus capsule/bowman’s capsule,
Renal medulla- proximal convoluted tubule, distal convoluted tubule, loop of Henley, collecting duct

Question 3

Describe the anatomical position

Answer 3

Below diaphragm and behind peritoneum

Question 4

Describe filtration

Answer 4

Takes place through the semipermeable walls of the glomerular capillaries and bowman’s capsule
Water and small molecules diffuse
Plasma proteins, blood cells and other large molecules stay in the blood

Question 5

Why does filtration take place?

Answer 5

There is a difference between blood pressure in the glomerulus and pressure of the filtrate in the bowman’s capsule

Question 6

Why is there a pressure difference

Answer 6

The efferent arteriole is narrower than the afferent arteriole so a capillary hydrostatic pressure builds up in the glomerulus. This pressure is bigger than the osmostic pressure by plasma proteins and filtrate hydrostatic pressure in bowman’s capsule , so fluid is pulled back into the bloodstream from the filtrate

Question 7

Describe auto regulation

Answer 7

Mechanism where renal blood flow is maintained at a constant pressure

Question 8

Outline selective reabsorption

Answer 8

reabsorption back into the blood
Most reabsorption of Water, electrolytes and nutrients (glucose and amino acids) takes place in PCT can be active and passive
Further reabsorption especially water, Na and Cl takes place in the loop but only 60-70% of filtrate reaches the loop
15-20% of filtrate reaches DCT, more electrolyte’s reabsorbed in DCT,
The filtrate entering the collecting ducts has become dilute and they reabsorbed as much water as necessary

Question 9

Describe transport maximum or renal threshold

Answer 9

If the level of a substance is above the transport maximum then it will appear in the urine as all the carrier sites in the nephron wall are overwhelmed

Question 10

Describe the role of anti diuretic hormone on selective reabsorption

Answer 10

ADH secreted by posterior pituitary, increases the permeability of the DCT and collecting ducts to water, increasing water reabsorption
osmoreceptors in the hypothalamus monitor water content of the blood and ADH is secreted according to that

Question 11

Describe the role of aldosterone on selective reabsorption

Answer 11

Secreted by adrenal cortex, it increases the reabsorption of Na and water and the excretion of K

Question 12

what is the importance of the kidney in pH regulation

Answer 12

in the PCT hydrogen ions are secreted into the filtrate, then combine with buffers, then excreted in urine as ammonium salts and hydrogen phosphate

Question 13

describe the renin-angiotensinogen mechanism and its function

Answer 13

cells in afferent arteriole release renin in response to low arteriole pressure, low blood volume and sympathetic NS
renin converts plasma protein angiotensingen to angiotensin 1 which is then converted by ACE to angiotensin 2
it is a powerful vasoconstrictor and increases blood pressure
stimulates the release of aldosterone from adrenal cortex to cause retension of Na and increased excretion of K